In Gainesville,
Florida, soil scientist L. Hartwell Allen measures heights of rice cultivars
grown in a temperature-gradient greenhouse to determine the effect of elevated
temperature on reproductive growth and seed yield. Click the image for more
information about it.

High Temperatures Could Leave Seed Crops
Sterile

Some crop plantslike rice, kidney beans, soybeans and
peanutsstop producing seeds when exposed to high temperatures.
Agricultural Research Service (ARS)
scientists in Gainesville, Fla., found that the higher temperatures affect
reproductive processes in the plants.

Increased temperatures affect reproductive processes more than they
affect photosynthesis and vegetative growth, according to Allen. A plant may
still grow to its typical size even if its seed development fails.

To evaluate heat tolerance of various cultivars, the scientists used
growth chambers under natural sunlight and greenhouses for a range of
temperatures. They measured heats effect on yields of rice, grain
sorghum, kidney beans, soybeans and peanuts grown at two levels of carbon
dioxide350 parts per million (ppm), which is near current levels of
atmospheric carbon dioxide, and 700 ppmand at four maximum/minimum daily
temperature cycles.

Each crop was found to have its own optimal mean daily temperature
(OMDT) for seed yield. As temperatures rose, yields decreased, dropping to zero
at about 18 degrees F above each crops specific OMDT. Seed productivity
generally decreased by about six percent for every one degree F above a given
plants OMDT, according to Allen.

For all the crops studied, even when pollination was successful,
shortened seed-filling time and higher respiration rates at moderate
temperature increases also contributed to yield declines.

Using traditional breeding to develop crops with built-in heat
tolerance may offer the best hope for helping plants--and growers--cope with
rising temperatures, according to Allen.

Read more
about the research in the August 2006 issue of Agricultural Research
magazine.